Additive manufacturing technology (AMT) low profile radiator

ABSTRACT

Described herein is a low profile radiator (LPR) manufactured using additive manufacturing technology (AMT). Such an AMT radiator is suitable for use in an array antenna which may be fabricated using AMT manufacturing processes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/584,264 filed Nov. 10, 2017, entitled ADDITIVE MANUFACTURINGTECHNOLOGY (AMT) LOW PROFILE RADIATOR and to U.S. Provisional PatentApplication No. 62/584,300 filed Nov. 10, 2017, entitled LOW PROFILEPHASED ARRAY, which are incorporated by reference herein in theirentirety.

GOVERNMENT RIGHTS

Not applicable.

BACKGROUND

As is known in the art, antenna or (radiator) designs commonly employ astandard printed circuit board (PCB) manufacturing process which relieson multiple process steps, expensive materials, and slow cycleturnaround time. Multiple process steps can be a driver for both highcost and slow turnaround time.

Furthermore, antenna assemblies are fabricated generally through aseries of processes (e.g., lamination, conductive via backfill) whichincreases labor cost of manufacturing the overall antenna assembly. Inaddition to such added labor costs, the use of multiple processes addscycle time which leads to long build times. Furthermore, if any circuitadjustments are needed, the use of multiple processes may extend anytroubleshooting phase. In addition, typical PCB processes do not allowfor the small feature sizes necessary to produce a thin array for spacebased applications.

SUMMARY

Described herein is a radiator having a thickness in the range of about0.020 inches (20 mils). Such a radiator is referred to as a low profileradiator and is suitable for use in an array antenna comprised of suchlow profile radiators. The low profile radiator (LPR) design describedherein is provided using additive manufacturing technology (AMT) andthus may be referred to as an AMT radiator. Such an AMT radiator issuitable for use in an array antenna which may be fabricated using AMTmanufacturing processes.

It has been recognized that radiator designs capable of beingmanufactured via an AMT approach are significantly lower cost inproduction, can be rapidly prototyped, and customized to meet designneeds. In addition, due to its low profile, the radiator describedherein is suitable for use in space-based applications.

Furthermore, the radiator described herein is suitable for use in afoldable array, having a launch volume (i.e., the volume which would beoccupied in a launch vehicle) and cost which are reduced compared to acost and volume required by prior art antennas having the same orsimilar operating characteristics. The radiator described herein is alsocapable of deploying in a low earth orbit (LEO) space environment. Thus,radiators of the type described herein are suitable for use in mobilesatellite systems (MSS).

Since the radiator design described herein may be manufactured usingAMT, the radiator described herein solves problems associated withradiators provided using conventional printed circuit board (PCB)manufacturing techniques. As noted above, the overall thickness of theradiator described herein can be confined to about 20 mils (508 microns)because the milling and printing capabilities of the AMT machines allowfor the smaller feature sizes needed for a low profile array. Featuresizes would include, but are not limited to, both the width oftransmission lines and the faraday walls (isolation elements) which canbe made smaller than with conventional methods.

Furthermore, the radiator described herein utilizes printed conductive“Faraday walls” which are disposed to confine electric fields in desiredregions of the radiator. Such Faraday walls can be produced in the samemanufacturing step as milling the other features. This saves significantlabor costs which drive down the overall cost of the assembly.

The radiator design described herein also utilizes AMT capabilities toprint conductive elements of virtually any shape and size, withinmachine constraints. These are used as tuning elements to achieve thedesired performance for the low profile array.

Finally, a custom printed connector interface is used so that a standardBMB connector can be used to test the device.

The radiator design described herein is provided from AMT single-stepmill and fill operations to produce a radiator having Faraday walls,vertical-launch connections, small (2×2 element) building blocks andmilled copper traces.

The AMT antenna is provided having a geometry which is relatively simplecompared with geometries of conventional radiators having similaroperating characteristics (e.g., operational frequency range, bandwidth,etc.). Furthermore, by using AMT manufacturing techniques, the antennamay include printed tuning elements having a shape and/or size needed toproduce double tuned performance.

Furthermore, the antenna design described herein can be integrated intofull arrays that can be printed and prototyped in short amount of time.

One aspect of the present disclosure is directed to an antenna elementmanufactured using additive manufacturing technology (AMT). In oneembodiment, the antenna element comprises a substrate having first andsecond opposing surface with a milled bowtie slot aperture provided inthe first surface thereof, and at least one Faraday wall disposedproximate the bowtie slot aperture.

Embodiments of the antenna element further may include the at least oneFaraday wall having a first one and a second one of a plurality ofFaraday walls. The plurality of Faraday walls may be symmetricallydisposed about the aperture with the first one of said plurality ofFaraday walls forming a first set of tuning elements symmetricallydisposed on either side of said bowtie slot radiator and the second oneof said plurality of Faraday walls forming a second set of tuningelements symmetrically disposed on either side of said bowtie slotradiator. The antenna element further may include a feed circuitcomprising a vertical launch extending from the first to second surfaceof said substrate and a feed line disposed across a slot portion of saidmilled aperture. The feed circuit may be disposed between the first setof tuning elements and the second set of tuning elements.

Another aspect of the disclosure is directed to an antenna assemblycomprising a substrate having first and second opposing surface with amilled aperture provided in the first surface thereof, a first set oftuning elements symmetrically disposed on either side of said milledaperture, a second set of tuning elements symmetrically disposed oneither side of said of said milled aperture, and a feed circuitcomprising a vertical launch extending from the first to second surfaceof said substrate and a feed line disposed across a slot portion of saidmilled aperture.

Embodiments further may include an array antenna having a plurality ofantenna assemblies. The antenna assembly may include four antennaassemblies arranged such that the first set of tuning elements of afirst antenna assembly and a first set of tuning elements of a secondantenna assembly are respectively adjacent to a second set of tuningelements of a third antenna assembly and a second set of tuning elementsof a fourth antenna assembly.

Yet another aspect of the disclosure is directed to an AMT process forfabricating a bowtie slot antenna. In one embodiment, the methodcomprises: (a) milling copper from a first surface of a double claddielectric substrate to form an aperture; (b) milling copper from asecond, opposite surface of the double clad dielectric substrate to forma feed line for the aperture; (c) bonding the double clad dielectricsubstrate to a first surface of a second substrate having a ground planeconductor disposed over a second surface thereof to for a bondedassembly; (d) milling the bonded assembly to form at least one openingfor a Faraday wall proximate the aperture; and (e) filling the at leastone opening with a conductive liquid to form the Faraday wall.

Embodiments of the method further may include mining the bonded assemblyto form at least one opening for a vertical signal path and filling theat least one opening for the vertical signal path. The conductive liquidmay be a conductive ink.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of at least one embodiment are discussed below withreference to the accompanying figures, which are not intended to bedrawn to scale. The figures are included to provide illustration and afurther understanding of the various aspects and embodiments, and areincorporated in and constitute a part of this specification, but are notintended as a definition of the limits of the disclosure. In thefigures, each identical or nearly identical component that isillustrated in various figures may be represented by a like numeral. Forpurposes of clarity, not every component may be labeled in every figure.The foregoing features may be more fully understood from the followingdescription of the drawings in which:

FIG. 1 is a top view of a bowtie radiator manufactured using additivemanufacturing technology (AMT);

FIG. 1A, is a plot of reflection coefficient (S11) at a radiatorinput/output port which illustrates a so-called “double tuning”characteristic achieved via tuning elements;

FIG. 1B is a top view of a plurality of bowtie radiators, which may bethe same as, or similar to, the bowtie radiator described in FIG. 1,disposed to form a 2×2 array antenna;

FIG. 2 is a model of a bowtie radiator field configuration achievedthrough the use of printed reactive tuning elements;

FIG. 3 is an isometric view of a bowtie radiator which may be the sameas, or similar to, the bowtie radiator described above in conjunctionwith FIG. 1;

FIG. 4 is a cross-sectional view of the bowtie radiator of FIG. 3 takenacross lines 4-4 in FIG. 3; and

FIGS. 5-5D are a series of diagrams illustrating a process to couple anaperture antenna to a feed line.

DETAILED DESCRIPTION

The concepts, systems and techniques described herein are directedtoward a phased array antenna provided using additive manufacturingtechnology so as to provide the phased array antenna having a lowprofile (i.e., a thickness in the range of about 15 mils to about 25mils (referred to herein as a low profile phased array).

It is to be appreciated that embodiments of the methods and apparatusesdiscussed herein are not limited in application to the details ofconstruction and the arrangement of components set forth in thefollowing description or illustrated in the accompanying drawings. Themethods and apparatuses are capable of implementation in otherembodiments and of being practiced or of being carried out in variousways. Examples of specific implementations are provided herein forillustrative purposes only and are not intended to be limiting. Also,the phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use herein of“including,” “comprising,” “having,” “containing,” “involving,” andvariations thereof is meant to encompass the items listed thereafter andequivalents thereof as well as additional items. References to “or” maybe construed as inclusive so that any terms described using “or” mayindicate any of a single, more than one, and all of the described terms.Any references to front and back, left and right, top and bottom, upperand lower, end, side, vertical and horizontal, and the like, areintended for convenience of description, not to limit the presentsystems and methods or their components to any one positional or spatialorientation.

Referring now to FIG. 1, a radiator 10 manufactured using an additivemanufacturing technology (AMT) manufacturing process includes a firstdielectric substrate 14 disposed over and bonded (or otherwise coupled)to a second dielectric substrate 15. A first surface 14 a of substrate14 is provided having an electrically conductive material 16 (e.g.,copper or an equivalent conductive material) disposed thereover (aportion of conductor 16 has here been removed to reveal a portion ofdielectric substrate surface 14 a).

An aperture antenna element 12 (or more simply “aperture” 12) having ageneral “bowtie” shape is milled into a surface 14 a of the firstdielectric substrate 14. The bowtie shaped aperture 12 is formed by anAMT milling operation which removes the conductive material 16 fromsubstrate surface 14 a to form the bowtie shape aperture 12. In someembodiments the conductive material 16 is provided as copper having athickness of 0.0007 inch (i.e., ½once (oz) copper) is disposed oversubstrate surface. In one particular embodiment, a central portion ofthe aperture 12 is provided having a width of about 7 mils (178microns). The width of aperture 12 is important in that it needs to beselected so as to properly excite the bowtie aperture. The particularaperture width is thus selected in accordance with a variety of factorsincluding, but not limited to, the desired frequency of operation (orfrequency bandwidth of operation), the thickness of substrates whichprovide the radiator and the particular shape of the aperture.

Furthermore, although in this illustrative embodiment conductor 16 isprovided as ½ oz copper, it should, of course, be appreciated that inother embodiments, other conductive materials (i.e., conductors otherthan copper) and other thicknesses (i.e., a conductor having a thicknessother than 0.0007 inch) may also be used.

Bowtie radiator 10 further includes first and second sets of tuningelements 18, 20. The first set of tuning elements 18 includes a twopairs of conductors 18 a, 18 b with each conductor in the pair having arectangular shape. The second set of tuning elements 20 includes a twopairs of conductors 20 a, 20 b with each conductor in the pair having asquare shape.

In some embodiments, the tuning elements 18 a, 18 b, 20 a, 20 b areformed by AMT milling and filling operations. The details of the AMToperations will be described hereinbelow. Suffice it here to say that inthe milling operation conductive material 16 as well as substratematerial 14 is removed so as to form an opening in the substrate havingthe desired shape of the tuning element (here, pairs of rectangular andsquare shapes generally denoted 18, 20, respectively). A conductive ink(or more generally a conductive fluid) is then disposed in the openingsto form the tuning elements 18, 20.

With this technique, radiator having a geometry which is relativelysimple compared with geometries of prior art radiators having similaroperational characteristics (e.g., frequencies of operation, bandwidthcharacteristics, gain characteristics, etc.) is provided.

The printed tuning elements can be of the shape or size needed toproduce double tuned performance. That is, as will be described below inconjunction with FIG. 2, two sets of tuning elements are used to producea desired field configuration in a unit cell.

Referring briefly to FIG. 1A, a plot reflection coefficient (S11) at aradiator input/output port illustrates the so-called “double tuningcharacteristic achieved via tuning elements 18, 20. As can be seen inFIG. 1A, tuning elements 18, 20 can be used to create two resonances atdifferent frequencies F1, F2 which are within a desired operatingfrequency band of the radiator 10.

Referring now to FIG. 1B, a plurality of, here four, bowtie radiators 10a-10 d, are disposed form an array antenna 30. In the illustration ofFIG. 1A, the four bowtie radiators 10 a-10 d are disposed to form a 2×2array. Those of ordinary skill in the art will appreciate, of course,that an size array or shape array may be formed via the radiators. Arrayantenna 30 may be used as a building block with which to build relativelarge array antennas (e.g., array antennas comprising tens, hundreds orthousands of antenna elements depending upon the needs of a particularapplication). Thus, the radiator design described above in conjunctionwith FIG. 1 can be integrated into full antenna arrays that can beprinted and prototyped in short amount of time.

Referring now to FIG. 2, a simulation of an AMT radiator of the typedescribed above in conjunction with FIG. 1 illustrates that printedreactive tuning elements (or tuning posts) 18, 20 produce a desiredfield configuration within an antenna unit cell. Thus, tuning elements18, 20 function as so-called Faraday walls so as to control and shapefield configurations within an antenna unit cell.

It should be appreciated that the design relies on AMT features. Forexample, a conductor having a relatively high conductivity (e.g., aconductivity substantially in the range of that of copper) is used incurrent carrying areas (e.g., transmission lines as compared to Faradaywalls).

A feed circuit 32 comprises a printed vertical-launch signal path 33 anda pad 34. Signals are coupled to/from radiator 12 via feed circuit 32.

Referring now to FIG. 3, in which like elements of FIGS. 1 and 2 areprovided having like reference designations, a bowtie radiator includesaperture 12, tuning structures 18, 20 and feed circuit 32 comprised ofvertical launch structure 33, feed point (or pad) 34 and transmissionline feed 36 which crosses bowtie aperture 12. It should be appreciatedthat transmission line feed 36 is disposed on a surface of substrate 14opposite the substrate surface on which aperture 12 is disposed. Thus,the voltage on the transmission line feed creates a voltage gradientwhich excites the aperture from beneath.

In an embodiment, an AMT aperture radiator may be formed as follows. Anantenna substrate 14 is provided having a conductor on both sidesthereof (i.e., the substrate is provided as a double clad substrate). Amilling operation is performed on one side of the substrate (e.g., firstsurface 14 a) in which an aperture (e.g., aperture 12) is formed byremoving the conductor (e.g., conductor 16 in FIG. 1) in the desiredshape of the aperture. On the second, opposite side of the substrate,all copper is milled away to leave a feedline (e.g., feedline 36 as maybe most clearly seen in FIG. 3).

The antenna substrate is then bonded to a second substrate 15 (sometimesreferred to as a ground plane substrate) at 39 to thus form a bondedassembly (as shown in FIG. 4). The second substrate has a conductor(e.g., a ground plane conductor 40) disposed on a surface thereofopposite the feed line.

A milling operation is performed to provide openings for Faraday walls(e.g., tuning elements 18 a, 18 b, 20 a, 20 b). Significantly, duringthe milling operation the substrate and bond materials are removed, butground plane conductor 40 is left intact. Thus, the milling operationmay be performed from the aperture side of the bonded substrates (i.e.,the milling is done on the same side of the bonded assembly on whichaperture conductor 16 is disposed).

A milling operation is also performed to provide an opening for avertical launch signal path (e.g., vertical launch 33). The milling forthe vertical launch opening is also performed from the aperture side ofthe bonded substrates (i.e., the milling is done on the same side of thebonded assembly on which aperture conductor 16 is disposed).

A milling operation is also performed to form a pad in ground plane 40in the region around the vertical launch opening. This milling operationis performed on the ground plane side of the bonded assembly (i.e., themilling is done on the same side of the bonded assembly on which groundplane conductor 40 is disposed).

The openings for the Faraday walls and the vertical launch are thenfilled with conductive inks to form Faraday walls 18 a, 18 b, 20 a, 20 band vertical launch 33. In another embodiment, a wire conductor mayconvey a signal “vertically” between layers of the substrate, and may beused to feed a signal to or from various other layers. Such a verticallaunch may be formed by machining a hole in one or more of thesubstrates, applying solder to one or more conductor surfaces, insertinga segment of wire (e.g., copper wire) into the hole, and reflowing thesolder to mechanically and electrically secure a connection.

Referring now to FIG. 4 in which like elements of FIG. 3 are providedhaving like reference designations, the antenna includes a ground planehaving a milled bowtie slot radiator provided therein. The bowtieradiator is fed via a transmission line coupled to a vertical launch.The structures are formed in a dielectric substrate having a thicknessof about 10 mils. The substrate is provided having a pair of milled andprinted Faraday walls formed therein.

FIGS. 5-5D below, describe structures and techniques to provide aconductive vertical launch that is additive, inexpensive, and removeselectro-deposition of copper from the PCB manufacturing process.

Turning now to FIGS. 5-5D, a technique for forming a conductive (e.g.,copper) vertical launch (such as vertical launch 33 described above inconjunction with FIGS. 3 and 4) for coupling an AMT aperture antenna(such as aperture antenna 12 described above in conjunction with FIG. 1)to an AMT feed circuit (such as feed circuit 36 described above inconjunction with FIGS. 3 and 4) begins by milling a bottom trace (i.e.,feed circuit line 36) into one side of a double cladded dielectric)(FIGS. 5 and 5A). FIG. 5 illustrates a double cladded dielectricsubstrate (aperture substrate).

FIG. 5A illustrates a mill aperture and feed line formed in the doublecladded dielectric substrate.

The antenna substrate is bonded to a ground plane substrate (FIG. 5B).

An opening or cavity leading to the feed line is milled, drilled orotherwise formed (FIG. 5C).

After forming the opening, a solder bump is disposed in the openingagain the feed line and a cylinder of copper (or other conductivematerial) is inserted until it touches the solder bump down below. Ithas been found that such a copper cylinder can be at least as small as 5mils in diameter, which is much smaller than a conventional process cancreate (FIG. 5D).

A soldering iron or other heat source is applied to the top of the pieceof inserted copper. Because of the small distance, heat is conducteddown the length of the copper which reflows the solder at the feed layerwhich forms the connection between the inserted piece of copper and thefeed line (FIG. 5D).

The Faraday wall is a conductor providing an electromagnetic boundary“vertically” through the substrates. As described herein, the Faradaywall may be formed by machining a trench through the substrates down toa ground plane and filling the trench with a conductive material, suchas a conductive ink applied with additive manufacturing techniques. Theconductive ink, when set, may form a substantially electricallycontinuous conductor. The trench in which the Faraday wall is formeddoes not have to pierce or go through the ground plane. The Faraday wallmay therefore be in electrical contact with the ground plane.Additionally, a top of the Faraday wall may be in electrical contactwith another ground plane, which may be accomplished by slightover-filling of the machined trench to ensure contact between theconductive ink and the ground plane and/or by application of solder, forexample. Positioning of the Faraday wall may be selected for itsinfluence on signal(s) conveyed by the feed circuit. In variousembodiments, a Faraday wall may be positioned to provide isolationwithout regard to influencing a signal in any particular way other thanto provide the isolation.

Having described preferred embodiments, which serve to illustratevarious concepts, structures and techniques, which are the subject ofthis patent, it will now become apparent to those of ordinary skill inthe art that other embodiments incorporating these concepts, structuresand techniques may be used. Additionally, elements of differentembodiments described herein may be combined to form other embodimentsnot specifically set forth above.

Accordingly, it is submitted that that scope of the patent should not belimited to the described embodiments but rather should be limited onlyby the spirit and scope of the following claims.

What is claimed is:
 1. An antenna element manufactured using additivemanufacturing technology (AMT), the antenna element comprising: asubstrate having first and second opposing surface with a bowtieaperture provided in the first surface thereof; and a plurality ofshielding elements disposed proximate the bowtie slot aperture, theplurality of shielding elements including a first one of a plurality ofshielding elements and a second one of a plurality of shieldingelements, the plurality of shielding elements being symmetricallydisposed about the aperture with the first ones of the plurality ofshielding elements forming a first set of tuning elements symmetricallydisposed on either side of the bowtie aperture and the second ones ofthe plurality of shielding elements forming a second set of tuningelements symmetrically disposed on either side of said bowtie aperture.2. The antenna element of claim 1, further comprising a feed circuitcomprising a vertical launch extending from the first to second surfaceof said substrate and a feed line disposed across a slot portion of saidmilled aperture.
 3. The antenna element of claim 2, wherein the feedcircuit is disposed between the first set of tuning elements and thesecond set of tuning elements.
 4. An AMT process for fabricating theantenna element of claim 1, the method comprising: (a) milling copperfrom a first surface of a double clad dielectric substrate to form anaperture; (b) milling copper from a second, opposite surface of thedouble clad dielectric substrate to form a feed line for the aperture;(c) bonding the double clad dielectric substrate to a first surface of asecond substrate having a ground plane conductor disposed over a secondsurface thereof to for a bonded assembly; (d) milling the bondedassembly to form at least one opening for a shielding element proximatethe aperture; and (e) filling the at least one opening with a conductiveliquid to form the shielding element.
 5. The method of claim 4, furthercomprising milling the bonded assembly to form at least one opening fora vertical signal path and filling the at least one opening for thevertical signal path.
 6. The method of claim 5, wherein the conductiveliquid is a conductive ink.